Composite Image of Abell 3376 (IMAGE) Chandra X-ray Center Caption This composite image of the galaxy cluster Abell 3376 shows Chandra and ROSAT X-ray data (gold), an optical image from the Digitized Sky Survey (red, green and blue), and a radio image from the VLA (blue). Two different teams used Chandra observations of galaxy clusters -- including Abell 3376 -- to study the properties of gravity on cosmic scales and test Einstein's theory of General Relativity. Such studies are crucial for understanding the evolution of the universe, both in the past and the future, and for probing the nature of dark energy, one of the biggest mysteries in science. Credit X-ray: NASA/CXC/SAO/A. Vikhlinin; ROSAT Optical: DSS Radio: NSF/NRAO/VLA/IUCAA/J.Bagchi Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.